A boy from Bensonhurst
Carl Edward Sagan was born on November 9, 1934, in Bensonhurst, Brooklyn, the son of Samuel Sagan, a garment worker who had emigrated from Kamianets-Podilskyi in what is now Ukraine, then part of the Russian Empire, and Rachel Molly Gruber, a New York housewife. He was named after his mother’s own mother, Chaiya Clara, who had died giving birth to her second child; Sagan later described her as the mother Rachel never knew. He had one sister, Carol.
Money was tight, but the household was rich in encouragement. His father, not especially religious, showed him compassion and a gentle wonder at the world; his mother, ambitious for her son, pushed him to excel. Sagan later said his parents, neither of them scientists, taught him the two habits of mind at the heart of science: scepticism and wonder.
Two childhood experiences fixed his course. At the 1939 New York World’s Fair, the four-year-old was dazzled by the futuristic exhibits and the burial of a time capsule; he later wrote that the world held wonders he had never guessed. A little later, at the local library, he asked for a book about stars and learned that they were distant suns, so far away that our own Sun would look like a point of light from them. The scale of it struck him, he said, with an almost religious force. Trips to the American Museum of Natural History and the Hayden Planetarium, and a steady diet of science fiction, did the rest.
Chicago and the planets
When he was fourteen the family moved to Rahway, New Jersey, where Sagan ran a chemistry club, built a home laboratory, and graduated from Rahway High School in 1951, voted by his classmates most likely to succeed. The family could not afford a private school, but at sixteen he entered the University of Chicago, then famous for admitting gifted teenagers.
Chicago gave him a broad liberal-arts grounding and then a scientific apprenticeship among giants. He studied with the Nobel laureates Harold Urey and H. J. Muller and, above all, with the planetary astronomer Gerard Kuiper, who taught him the art of the quick, back-of-the-envelope calculation. He earned a bachelor’s degree in physics in 1955, a master’s in 1956, and in 1960 a doctorate in astronomy and astrophysics with a dissertation, supervised by Kuiper, titled “Physical Studies of the Planets.”
After a Miller fellowship at the University of California, Berkeley, he taught and researched at Harvard from 1963. In 1968 Harvard denied him tenure, a decision he did not expect; colleagues had grumbled about the breadth of his interests and his growing public profile, and Urey himself wrote against him. Cornell, at the invitation of the astronomer Thomas Gold, took him in. He became a full professor in 1970, directed its Laboratory for Planetary Studies, and in 1976 was named David Duncan Professor of Astronomy and Space Sciences, a chair he held until his death.
Reading the neighbouring worlds
Sagan’s own research reshaped the picture of the solar system at the very moment spacecraft first reached it. Many scientists had imagined Venus as a steamy, perhaps habitable world. From radio observations, Sagan estimated a surface temperature of around 500 °C and argued that a runaway greenhouse effect in its thick carbon-dioxide atmosphere was to blame. NASA’s Mariner 2 confirmed the extreme heat in 1962. The lesson, that an atmosphere can trap enough heat to sterilise a planet, later became part of how scientists explained climate change on Earth.
On Mars he helped dispel another romantic idea. The seasonal light and dark patches that some astronomers took for spreading vegetation, he and his colleagues argued, were shifts in dust driven by windstorms, an interpretation the Mariner 9 orbiter supported. He suggested that Saturn’s moon Titan might have liquids on its surface and that its reddish haze was made of complex organic molecules, and that Jupiter’s moon Europa might hide an ocean beneath its ice, an idea later supported by the Galileo spacecraft.
He was an adviser to NASA from the 1950s, briefed Apollo astronauts before their flights to the Moon, and served as an experimenter on the Mariner, Viking, Voyager and Galileo missions. He was also among the first serious scientists to champion the search for extraterrestrial intelligence. In 1982 he organised a petition in Science supporting SETI, signed by seventy scientists including seven Nobel laureates.
Messages in bottles
Sagan understood that spacecraft were also messages. For Pioneer 10, launched in 1972, and Pioneer 11, launched in 1973, he and the astronomer Frank Drake designed a gold-anodised plaque showing a man and a woman, drawn by the artist Linda Salzman Sagan, together with a map locating the Sun among nearby pulsars. Both probes are now leaving the solar system.
For the two Voyager spacecraft of 1977 he went further. He chaired the committee that assembled the Voyager Golden Record, a gold-plated copper phonograph disc carrying greetings in fifty-five languages, the sounds of wind, rain and a heartbeat, music from Bach and Beethoven to Chuck Berry and traditional songs from around the world, and more than a hundred images of life on Earth. Its creative director was the writer Ann Druyan, who would become his third wife.
Years later, as Voyager 1 sped beyond the outer planets, Sagan persuaded NASA to turn its cameras back towards home. On February 14, 1990, from about six billion kilometres away, it photographed Earth as a speck less than a pixel wide in a scattered beam of sunlight. Sagan named it the Pale Blue Dot and made it the centre of a famous meditation on human pride, cruelty and responsibility: there is no one else, he argued, to save us from ourselves.
Cosmos
Sagan had begun writing for the general public in the 1970s with The Cosmic Connection, and in 1978 his book The Dragons of Eden, an exploration of the evolution of human intelligence that introduced his Cosmic Calendar, won the Pulitzer Prize for General Nonfiction. But his great work of public education came in 1980.
Cosmos: A Personal Voyage, a thirteen-part series written with Ann Druyan and the astronomer Steven Soter and broadcast on PBS from September 1980, took viewers from the library of ancient Alexandria to the edge of the observable universe. Its host, in a turtleneck and corduroy jacket, explained evolution, relativity and the life cycles of stars with an unhurried delight that made science feel like a shared human story rather than a list of facts. The series won Emmy and Peabody awards and has been seen by at least 500 million people in sixty countries. The companion book became the best-selling science book ever published in English up to that time.
Cosmos made Sagan the most recognised scientist in America, a regular guest on television talk shows and the subject of affectionate parody. Some colleagues resented his celebrity; in the early 1990s he was not elected to the National Academy of Sciences, reportedly because of that resentment, though in 1994 the Academy awarded him its Public Welfare Medal. Generations of astronomers, physicists and engineers have said that it was Cosmos that drew them into science.
Nuclear winter and the baloney detection kit
Sagan believed that scientists had a duty to speak about the dangers their knowledge revealed. In 1983 he was one of five authors, with Richard Turco, Owen Toon, Thomas Ackerman and James Pollack, of the so-called TTAPS study, which argued that smoke and soot from cities burning in a nuclear war could darken and chill the planet, causing crop failures far beyond the battlefields. The phrase “nuclear winter” coined by Turco, entered public debate. Sagan campaigned against the arms race and against President Reagan’s Strategic Defense Initiative, and wrote The Cold and the Dark (1984) and A Path Where No Man Thought (1990). Critics, including the physicist Edward Teller, accused him of overstating the science for political ends, and later models suggested milder effects than the first estimates; but the core idea has been refined rather than abandoned, and in 2022 Sagan was posthumously honoured with the Future of Life Award for the work.
He was equally passionate about clear thinking. He popularised the principle that “extraordinary claims require extraordinary evidence” and in The Demon-Haunted World (1995) offered a “baloney detection kit” for testing claims about UFOs, psychics and pseudoscience, while warning of a society that depends on science and technology but understands little of either. His only novel, Contact (1985), imagined humanity’s first radio message from another civilisation; for its fictional wormhole he consulted the physicist Kip Thorne, sparking real research. It became a 1997 film starring Jodie Foster. In 1980 he co-founded the Planetary Society, today one of the world’s largest space-advocacy organisations, and served as its first president.
A Jewish home and a questioning mind
Sagan grew up in a Reform Jewish family. His mother believed in God and was active in the temple; his father was not particularly observant. Carl had his bar mitzvah at thirteen, and as a high-school student he won an essay contest writing about poets and the Bible. He was the son of an immigrant from the Jewish heartland of the Russian Empire, part of a generation of children of Eastern European Jewish immigrants who rose through New York’s public schools and the great universities into American science.
As an adult he did not practise any religion, and he resisted labels. He called himself an agnostic, explaining that he knew of no compelling evidence that God existed but also none for the certainty an atheist claims. Speaking of God at all, he preferred the sense of Spinoza and Einstein: the sum of the laws that govern the universe. In his 1985 Gifford Lectures, later edited by Ann Druyan as The Varieties of Scientific Experience, he argued that science itself could be a profound source of spirituality, an awe made larger, not smaller, by understanding.
Family, illness and farewell
Sagan married three times. With the biologist Lynn Margulis, whom he married in 1957, he had two sons, Dorion and Jeremy; with the artist Linda Salzman, married in 1968, he had a son, Nick; and with Ann Druyan, his collaborator on Cosmos and the Golden Record, married in 1981, he had a daughter, Sasha, and a son, Sam. He and Druyan wrote several books together, and she remained the steward of his work for decades after his death.
In the mid-1990s he was diagnosed with myelodysplasia, a disease of the bone marrow. Over two years he underwent three bone-marrow transplants, with his sister as donor, and kept writing throughout. He died of pneumonia at the Fred Hutchinson Cancer Research Center in Seattle on December 20, 1996, at the age of sixty-two, and was buried at Lake View Cemetery in Ithaca, New York. His last book, the essay collection Billions and Billions, appeared the following year.
Legacy
In July 1997 NASA renamed the landing site of its Mars Pathfinder mission the Carl Sagan Memorial Station, and the asteroid 2709 Sagan bears his name. In 2014 Ann Druyan and the producer Seth MacFarlane brought Cosmos back to television as Cosmos: A Spacetime Odyssey, hosted by Neil deGrasse Tyson, who as a teenager had been invited by Sagan to visit him at Cornell.
Sagan’s scientific achievements, from the Venus greenhouse to the dust storms of Mars, would have been enough for a distinguished career. His larger gift was to make the universe feel like the public’s own inheritance. He showed millions of people that the atoms in their bodies were forged in stars, that their home was a mote in a sunbeam, and that the best way to honour that home was to look at it honestly, with wonder and with doubt.
Sources & further reading
Carl Sagan, Wikipedia · Carl Sagan, The Planetary Society · Carl Sagan, Pioneering US Astrophysicist with Ukrainian Connections, Kyiv Post · Carl Sagan, Wikiquote · Researched from the sources above and checked against them. Spotted an error? Tell us.
A life of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.